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All sudoku puzzles in this forum post are the intellectual property of Børge Alexander Tetlie Anderssen.
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There are three difficulties to choose from.
All three puzzles have the same solution.

The difficulty levels explained     The ratings explained

A) Novice.
B) Apprentice (mainstream edition).
C) Master (38 Intersection, 3 Naked Pair, 1 Uniqueness Test 3 on {56) in g2, 1 Finned X-Wing on 2 in g3, 1 X-Wing on 2 in g3). Select to view details.
The advanced techniques are needed in 2 different grids.



Regular Samurai #79A (Novice)

Rating based on required solving techniques:  Moderate

800100000600002830020050009000645000017000000000000328000003000540090000080500000
001000009000010000700005204000000000800020431500460000000000080000037000000000070
000090000000000000000002000400356070000000800100780006000900000000020000000003000
500000000080094000000600000000050190056000003240010000007000950008705002300902000
000000170000020000000030000000001006900000503100040000070006050005000890000079030



Regular Samurai #79B (Apprentice)

Rating based on required solving techniques:  Hard

850100000600000830020050009008640000017000000000000020000003000540090000000500000
001000009000010000700005204900000000800020431500460000000000080000037000000000070
000098000000000000000000000408356070000000000100780006000900000000020000000003000
500000000002090000000600000000050190006000003240010000000000950008700032300902000
000000170000020000000030000000000086900000503100040000070006050005000890000079000



Regular Samurai #79C (Master)

Rating based on required solving techniques:  Ultra Hard

850100000600000830020050009008640000017000000000000328000003000540090000000500000
001000009000010000700005204900000000800020431500460000000000080000037000000000070
000098000000000000000002000400356070000000800100780006000900000000020000000003000
500000000002090000000600000000050190006000003240010000000000950008700002300902000
000000170000020000000030000000000086900000503100040000070006050005000890000079000

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Don't know if there is any protocol for posting a solution for one of these Masters. I'll try this and see if there are any concerns or better ideas. I've let SudokuSolver do All Simpler (SSAS) using the attached routine order in order to get to the interesting stuff. I don't solve like this since not all of it is simple for me to find.
Note: you can download the Routine order to your computer then click Solver-Options-Import into SudokuSolver.

G1 etc refers to the grid number. I'm assuming the middle grid is G3 and see that SS does this too.

In case anyone is interested, the SudokuSolver score is 2.61, much higher than the Apprentice version of 0.74. Felt much harder too!

It's possible I've been tricked with steps 1 and 2 since they involve cells in the overlapping nonets. Please post if it's wrong.

Regular Samurai #79C (Master) Key eliminations only Solution

Really hard puzzle. Thanks Børge.
Ed

Ed,

Thanks for your feedback and WT.

Hopefully this will become a regular event.

I rated this puzzle "Ultra Hard", which is the topmost (most difficult) rating for a Master level puzzle. So it should be hard, mainly due to the Uniqueness Test 3, which is a tricky technique to spot and use correctly. And it is required pretty early on, making it even more difficult to spot.

The other possible ratings for a Master level puzzle are "Very Hard", "Extra Hard" and "Super Hard". When generating a Regular Samurai puzzle, which is a semi-manual-automatic process, I try to vary the difficulty level. But I normally use the first suitable puzzle generated. Due to the lack of enthusiastic feedback, I do not feel overly inspired to put in more effort than absolutely necessary to get a suitable puzzle.

Corrected for some misspelled column numbers in 1/1a your WT is correct:

Here my WT:

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